1. Field of the Invention
This invention relates in general to gate valve seat seals, and in particular to a metal seat seal that has a flexible sealing edge to form a dual seal.
2. Description of the Prior Art
Gate valves have been used on subsea wellhead assemblies for a number of purposes. In such service usage, gate valves have been required to provide reliable sealing under harsh service conditions, which include high pressure, wide temperature ranges, the presence of corrosive fluids, sand particles, debris and the like. A number of gate valves have used various forms of seals which have been formed of elastomeric or other non-metallic materials and fitted at the locations required for sealing against fluid leakage. However, so far as is known, such non-metallic seals have been regarded as often failing to meet the requirement of sealing under harsh service conditions.